1. Field of the Invention
This invention concerns an arrangement to extract air from a crankcase of an internal combustion engine of the substantially throttless type.
2. Description of Related Art
There are various known arrangements for extracting air from engine crankcases. German Utility Model 18 31 027 describes, for example, such an arrangement having an air conduit extending from the crankcase to an intake fitting formed to the engine air filter assembly. This arrangement achieves a relatively high negative pressure in the conduit relative to the crankcase which results in desired air extraction therefrom.
Likewise, German DE-B 14 76 052 describes an air extracting arrangement for a crankcase of an internal combustion engine having a carburetor. A filter cap allows air to enter the crankcase and an extraction line withdraws air therefrom to the narrowest position of the carburetor's venturi. A control mechanism is used to regulate air flow.
Further, in the extracting arrangement for air disclosed in German DE 37 26 332 C1, a crankcase extraction line is connected to a throttle housing and specifically to a trough-like depression formed therein. This construction allows condensation which may form particularly during idling of the engine to collect in this depression rather than on the throttle itself.
In the carburetor or manifold-injection fitted type of internal combustion engines described above, a difference in pressure between the throttle and crankcase regions is utilised in order to purge crankcase air. Typically, an outlet fitting on the cylinder head valve cover is utilised as an exit for air withdrawn from the engine. The extracted air includes so-called blow-by gases (about the pistons and piston rings). It is desirable to remove these blow-by gases because they are abrasive and promote engine wear of pistons and cylinders.